U.S. patent number 10,265,200 [Application Number 13/814,179] was granted by the patent office on 2019-04-23 for medical prostheses having bundled and non-bundled regions.
This patent grant is currently assigned to COOK MEDICAL TECHNOLOGIES LLC. The grantee listed for this patent is Steven J. Charlebois, William Kurt Dierking, Matthew S. Huser, Keith Milner, Jichao Sun. Invention is credited to Steven J. Charlebois, William Kurt Dierking, Matthew S. Huser, Keith Milner, Jichao Sun.
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United States Patent |
10,265,200 |
Charlebois , et al. |
April 23, 2019 |
Medical prostheses having bundled and non-bundled regions
Abstract
The present embodiments provide an endoluminal prosthesis, such
as a stent-graft, having a relatively low delivery profile. In one
embodiment, the prosthesis comprises a membrane, and at least one
stent having contracted and expanded states, where the stent is
coupled to the membrane and maintains patency in the expanded
state. The prosthesis further may comprise selectively oriented
axial and/or circumferential fibers arranged at predetermined
locations along the length and circumference of the prosthesis. An
increased population density of the circumferential and/or axial
fibers may be provided in areas in which the at least one stent
portion is attached to the membrane, or in areas of higher
physiological loads imposed upon the endoluminal prosthesis.
Selectively orienting axial fibers and circumferential fibers at
predetermined locations along the length and circumference of the
prosthesis, but not continuously along the entire prosthesis,
significantly reduces delivery profile due to the reduction in
graft material.
Inventors: |
Charlebois; Steven J. (West
Lafayette, IN), Dierking; William Kurt (Louisville, KY),
Huser; Matthew S. (West Lafayette, IN), Milner; Keith
(West Lafayette, IN), Sun; Jichao (West Lafayette, IN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Charlebois; Steven J.
Dierking; William Kurt
Huser; Matthew S.
Milner; Keith
Sun; Jichao |
West Lafayette
Louisville
West Lafayette
West Lafayette
West Lafayette |
IN
KY
IN
IN
IN |
US
US
US
US
US |
|
|
Assignee: |
COOK MEDICAL TECHNOLOGIES LLC
(Bloomington, IN)
|
Family
ID: |
45567880 |
Appl.
No.: |
13/814,179 |
Filed: |
August 10, 2010 |
PCT
Filed: |
August 10, 2010 |
PCT No.: |
PCT/US2010/044984 |
371(c)(1),(2),(4) Date: |
May 06, 2013 |
PCT
Pub. No.: |
WO2012/021125 |
PCT
Pub. Date: |
February 16, 2012 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20130211497 A1 |
Aug 15, 2013 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F
2/07 (20130101); A61F 2/82 (20130101); A61F
2/89 (20130101); A61F 2002/075 (20130101); A61F
2250/0028 (20130101); A61F 2250/0017 (20130101) |
Current International
Class: |
A61F
2/82 (20130101); A61F 2/07 (20130101); A61F
2/89 (20130101) |
Field of
Search: |
;623/1.13,1.15,1.16,1.32-1.33 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
International search report and written opinion for
PCT/US2010/044984 dated Oct. 7, 2010, 15 pgs. cited by applicant
.
Murray et al, "Vascular Graft Healing. III. FTIR Analysis of ePTFE
Graft Samples From Implanted Bigrafts", J. Biomed Mater Res B Appl
Biomater, Aug. 15, 2004; 70(2), Abstract, 1 pg. cited by applicant
.
International Preliminary Report on Patentability for
PCT/US2010/044984 dated Feb. 21, 2013, 12 pgs. cited by applicant
.
Supplemental European Search Report for European Patent Application
No. 10855978.2 dated Feb. 25, 2014, 8 pgs. cited by applicant .
Response to Office Action for European Patent Application No.
10855978.2 dated Sep. 4, 2014, 6 pgs. cited by applicant .
Decision to Grant EP10855978.2 dated Oct. 16, 2015, 31 pgs. cited
by applicant .
Extended European Search Report for Ep 16156978.5 dated Jun. 1,
2016, 8 pgs. cited by applicant.
|
Primary Examiner: Lopez; Leslie
Attorney, Agent or Firm: Brinks Gilson & Lione
Claims
We claim:
1. An endoluminal prosthesis, comprising: a membrane having a lumen
for allowing fluid flow; and a plurality of circumferential fibers
coupled to the membrane that form at least one bundled region in
which at least two adjacent circumferential fibers are separated by
a first spacing, and that form at least one-non-bundled region in
which at least another two adjacent circumferential fibers are
separated by a second spacing, where the first spacing is less than
the second spacing, the second spacing is at least three times
greater than the first spacing, and the circumferential fibers are
not interwoven with any other fiber, and where each of the
plurality of circumferential fibers extends around an entire
circumference of the membrane.
2. The endoluminal prosthesis of claim 1 where at least one stent
is coupled to the membrane using sutures only in at least one of
the bundled regions.
3. The endoluminal prosthesis of claim 2 where the stent comprises
a zig-zag shape having proximal and distal apices, where at least
one of the proximal apices of the stent is secured to the membrane
at a proximal bundled region, and where at least one of the distal
apices of the stent is secured to the membrane at a distal bundled
region, where the proximal and distal bundled regions are separated
by at least one non-bundled region.
4. The endoluminal prosthesis of claim 1, further comprising a
plurality of axial fibers extending in a direction that is
generally parallel to a longitudinal axis of the endoluminal
prosthesis.
5. The endoluminal prosthesis of claim 4, where the plurality of
axial fibers overlap with at least one bundled region of
circumferential fibers at intersections, and where at least one
portion of a stent is secured to the membrane at one of the
intersections.
6. An endoluminal prosthesis, comprising: a membrane having a lumen
for allowing fluid flow; a plurality of axial fibers extending
generally along a longitudinal axis of the endoluminal prosthesis,
where each of the plurality of axial fibers are separated from one
another by a spacing, and each of the plurality of axial fibers
extends along the length of the membrane; and a plurality of
circumferential fibers disposed generally perpendicular to the
plurality of axial fibers, where at least one circumferential fiber
is separated from a first adjacent circumferential fiber by a first
spacing, and where the at least one circumferential fiber is
separated from a second adjacent circumferential fiber by a second
spacing, where the second spacing is at least three times greater
than the first spacing, and the circumferential fibers are not
interwoven with any other fiber, and where each of the plurality of
circumferential fibers extends around an entire circumference of
the membrane.
7. The endoluminal prosthesis of claim 6 where at least one axial
fiber is separated from a first adjacent axial fiber by a first
spacing of axial fibers, and where the at least one axial fiber is
separated from a second adjacent axial fiber by a second spacing of
axial fibers, where the first spacing of axial fibers is less than
the second spacing of axial fibers.
8. The endoluminal prosthesis of claim 7 where at least one stent
is coupled to the membrane at an intersection where the at least
one axial fiber and the first adjacent axial fiber meet at least
one of the circumferential fibers.
9. An endoluminal prosthesis, comprising: a membrane having a lumen
for allowing fluid flow; a plurality of circumferential fibers
coupled to the membrane that form at least one bundled region in
which at least two adjacent circumferential fibers are separated by
a first spacing, and that form at least two non-bundled regions
where in each of the non-bundled regions at least another two
adjacent circumferential fibers are separated by a second spacing,
where the first spacing is less than the second spacing; at least
one stent, where the at least one stent is sutured to the membrane
only at the bundled regions; and a plurality of axial fibers
extending generally along a longitudinal axis of the endoluminal
prosthesis, where at least one axial fiber is separated from a
first adjacent axial fiber by a first spacing of adjacent axial
fibers, and where at least one axial fiber is separated from a
second adjacent axial fiber by a second spacing of adjacent axial
fibers, wherein the stent comprises a plurality of proximal and
distal apices and wherein at least one of the proximal and distal
apices of the stent is aligned with at least one axial fiber.
10. The endoluminal prosthesis of claim 9 wherein the second
spacing is at least three times greater than the first spacing.
11. The endoluminal prosthesis of claim 9 where the at least one
stent is coupled to the membrane at an intersection where at least
one axial fiber meets at least one of the circumferential
fibers.
12. The endoluminal prosthesis of claim 9 wherein the first spacing
of adjacent axial fibers is substantially equal to the second
spacing of adjacent axial fibers.
13. The endoluminal prosthesis of claim 9 wherein the first spacing
of adjacent axial fibers is less than the second spacing of
adjacent axial fibers.
14. The endoluminal prosthesis of claim 9 wherein the membrane has
an interior surface and an exterior surface and wherein at least
one axial fiber is disposed on the exterior surface of the
membrane.
15. The endoluminal prosthesis of claim 14 wherein the at least one
stent is disposed between the interior surface of the membrane and
the at least one axial fiber.
16. The endoluminal prosthesis of claim 9 wherein a film is
disposed over the at least one axial fiber thereby encapsulating
the fiber between the membrane and the film.
17. The endoluminal prosthesis of claim 16 wherein the film
comprises a polymeric material.
Description
RELATED APPLICATIONS
The present patent document is a .sctn. 371 filing based on PCT
Application Serial No. PCT/US2010/0044984, filed Aug. 10, 2010 (and
published as WO 2012/021125A1 on Feb. 16, 2012), designating the
United States and published in English, which is hereby
incorporated by reference in its entirety.
BACKGROUND
Apparatus and methods for treating vascular conditions, and more
specifically, materials for use in treating such conditions, are
described.
Stent-graft assemblies may be used to treat a number of medical
conditions. One common use of stent-graft assemblies relates to the
treatment of an aneurysm, which is an abnormal widening or
ballooning of a portion of an artery that may be caused by a
weakness in the blood vessel wall. In many cases, the internal
bleeding is so massive that a patient can die within minutes of an
aneurysm rupture. For example, in the case of aortic aneurysms, the
survival rate after a rupture may be as low as 20%.
In an endovascular treatment of a blood vessel using a stent-graft,
the stent-graft is positioned in the blood vessel across the
aneurysm, e.g., using catheter-based placement techniques. The
stent-graft treats the aneurysm by sealing the wall of the blood
vessel with a generally impermeable graft material. Thus, the
aneurysm is sealed off and blood flow is kept within the primary
passageway of the blood vessel. Although stent-grafts are
frequently used for treating aneurysms, other medical treatments
also use stent-grafts and still other uses are possible, such as
uses for treating aortic dissections, stenosed arteries or other
conditions.
Various types of stent-grafts are constructed with a stent disposed
inside graft material, outside of graft material, or between inner
and outer layers of graft material. The stents commonly are coupled
to the one or more layers of graft material. For example, one
technique for securing graft material to a stent involves securing
one or more graft layers to the struts of the stent.
Another technique that is used for securing graft layers to a stent
generally involves encapsulating the stent or a portion thereof
with an inner and an outer layer of graft material. In this type of
stent-graft, the two layers of graft material are adhered to each
other through open areas in the stent structure. Some additional
bonding may also occur between each graft layer and the stent
structure itself, for example, the inner and outer graft layers may
be adhered by heating or using adhesives.
In constructing stent-grafts, it may be difficult to furnish a
reliable prosthesis having a relatively small diameter delivery
profile, such that the prosthesis may be delivered into smaller
vessels. Notably, the inventors have determined that the fabric
portion of a stent-graft can contribute significantly to the
overall delivery profile of a stent-graft. For example, graft
material, depending on its thickness, may contribute between about
50-80% of the overall volume of a stent-graft's profile in a
delivery configuration. Thus, such relatively large prostheses may
not be capable of delivery into smaller vessels. However, the
fabric used in stent-grafts for endovascular graft repair must
maintain important and unique requirements, including sufficient
tensile strength, permeability, biocompatibility, and overall bulk,
and such properties should not be compromised in order to achieve
the desired smaller profile.
SUMMARY
The present embodiments provide an endoluminal prosthesis having
beneficial properties and a relatively low delivery profile.
In a first embodiment, the prosthesis comprises a membrane having a
lumen for carrying fluid flow, and further comprises a plurality of
circumferential fibers coupled to the membrane. The plurality of
circumferential fibers form at least one bundled region in which at
least two adjacent circumferential fibers are separated by a first
spacing, and form at least one non-bundled region in which at least
two adjacent circumferential fibers are separated by a second
spacing, where the first spacing is less than the second spacing.
In one example, the second spacing in the non-bundled region is at
least three times greater than the first spacing in the bundled
region.
In one embodiment, at least one stent is coupled to the membrane in
at least one bundled region of the stent. By way of example, where
the stent comprises a zig-zag shape having proximal and distal
apices, at least one of the proximal apices of the stent is secured
to the membrane at a proximal bundled region, and at least one of
the distal apices of the stent is secured to the membrane at a
distal bundled region. The proximal and distal bundled regions may
be separated by at least one non-bundled region.
A plurality of axial fibers also may be provided that extend in a
direction that is generally parallel to a longitudinal axis of the
endoluminal prosthesis. The plurality of axial fibers may overlap
with at least one bundled region of circumferential fibers at
intersections, and at least one portion of the stent may be secured
to the membrane at one of the intersections. Optionally, a
plurality of angled axial fibers also may be selectively
provided.
Advantageously, by selectively orienting circumferential fibers
and/or axial fibers at predetermined locations along the length and
circumference of the prosthesis, a specifically reinforced
prosthesis may be provided. For example, an increased population
density of the circumferential fibers and/or the axial fibers may
be provided in areas in which the at least one stent portion is
attached to the membrane. As another example, an increased
population density of the circumferential and/or axial fibers may
be provided in areas of higher physiological loads imposed upon the
endoluminal prosthesis. Thus, by selectively orienting axial fibers
and circumferential fibers at predetermined locations along the
length and circumference of the prosthesis, but not continuously
along the entire graft, a significantly reduced delivery profile
may be achieved due to the reduction in graft material. However,
strength and integrity characteristics of the stent-graft are
maintained.
Other systems, methods, features and advantages of the invention
will be, or will become, apparent to one with skill in the art upon
examination of the following figures and detailed description. It
is intended that all such additional systems, methods, features and
advantages be within the scope of the invention, and be encompassed
by the following claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be better understood with reference to the
following drawings and description. The components in the figures
are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Moreover, in the
figures, like referenced numerals designate corresponding parts
throughout the different views.
FIG. 1 is side view of a stent-graft according to a first
embodiment with stents removed for illustrative purposes.
FIG. 2 is side view of the stent-graft of FIG. 1 with stents
shown.
FIG. 3 is a side view of a proximal portion of a stent-graft
provided in accordance with an alternative embodiment.
FIG. 4 is a side view of a proximal portion of a stent-graft
provided in accordance with a further alternative embodiment.
FIGS. 5-7 are side views of portions of various stent-grafts
provided in accordance with further alternative embodiments.
FIG. 8 is a side view of a proximal portion of a stent-graft
provided in accordance with a further alternative embodiment.
FIGS. 9A-9C illustrative exemplary methods steps for manufacturing
a further alternative stent-graft.
FIG. 10 is side view of a stent-graft according to a further
alternative embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the present application, the term "proximal" refers to a
direction that is generally closest to the heart during a medical
procedure, while the term "distal" refers to a direction that is
furthest from the heart during a medical procedure.
Referring now to FIGS. 1-2, a first embodiment of a stent-graft 20
is shown. As shown in FIG. 1, the stent-graft 20 comprises a
membrane 25 having proximal and distal ends 22 and 24,
respectively, and a lumen 29 extending therebetween that is
dimensioned for fluid flow for a given application.
The stent-graft 20 further comprises at least one axial fiber 27
and at least one circumferential fiber 28. Preferably, a plurality
of axial fibers 27 and circumferential fibers 28 are provided, and
are arranged in predetermined patterns for one or more desired
functions, such as providing stent attachment locations and/or
being positioned in regions along the stent-graft 20 that are
subject to relatively high hydrodynamic forces, as explained
further below. For example, the axial fibers 27 may assist in
withstanding longitudinally-oriented blood flow forces, while the
circumferential fibers 28 may assist in withstanding pulsatile flow
forces.
Advantageously, by selectively orienting the axial fibers 27 and
circumferential fibers 28 at predetermined locations along the
length and circumference of the stent-graft 20, but not
continuously along the entire stent-graft, a significantly reduced
delivery profile may be achieved due to the reduction in fiber
material.
In the exemplary embodiment of FIGS. 1-2, the stent-graft 20
comprises a plurality of distinct regions, each for accommodating a
stent or portion of a stent. By way of example, four distinct
regions 30, 40, 50 and 60 are provided for accommodating stents 38,
48, 58 and 68, respectively. Each of the four distinct regions 30,
40, 50 and 60 comprises a predetermined arrangement of axial fibers
27 and circumferential fibers 28 for accommodating the respective
stents 38, 48, 58 and 68.
For example, the first distinct region 30 may be disposed near the
proximal end 22 of the prosthesis. As shown in FIG. 1, the first
distinct region 30 comprises a plurality of circumferential fibers
28 arranged in predetermined orientations. In particular, a
proximal bundled region 31 of the first distinct region 30
comprises multiple circumferential fibers 28 coupled to the
membrane 25. The circumferential fibers 28 are arranged such that
at least two adjacent circumferential fibers 28 within the proximal
bundle 31 are separated by a first spacing.
The first distinct region 30 further comprises a distal bundled
region 37 that, like the proximal bundled region 31, comprises at
least two adjacent circumferential fibers 28 separated by the same
first spacing as the proximal bundled region 31. The proximal and
distal bundled regions 31 and 37 may comprise a desired number of
circumferential threads per inch ("TPI").
The first distinct region 30 further comprises at least one
non-bundled region 34, which is disposed between the proximal and
distal bundled regions 31 and 37. The non-bundled region 34
comprises at least two adjacent circumferential fibers 28 that are
separated by a second spacing, which is greater than the first
spacing. In other words, as depicted in FIGS. 1-2, at least some,
if not all, of the circumferential fibers 28 of the non-bundled
region 34 are separated by a greater spacing as compared to the
circumferential fibers 28 of the proximal and distal bundled
regions 31 and 37. Notably, in one embodiment, the first spacing
may be zero, i.e., there is no separation of fibers.
In the example of FIGS. 1-2, the proximal and distal bundles 31 and
37 may have a greater TPI count of circumferential fibers 28
relative to the non-bundled region 34. Solely by way of example,
and without limitation, the proximal and distal bundled regions 31
and 37 may have a thread count between about 20 to about 120 TPI.
In contrast, the non-bundled region 34 may have a thread count of
less than 20 TPI. Therefore, in this example, there is a
non-uniform circumferential fiber population density along at least
a portion of the stent-graft 20. Additionally, the number of fibers
in each of the bundled and non-bundled regions may also vary. For
example, one bundled region may have more fibers than another
bundled region, and similarly for the non-bundled regions.
In one example, the first spacing within the proximal and distal
bundled regions 31 and 37 may be such that the spacing between
individual circumferential fibers 28 is less than or equal to the
width of the fibers themselves. Thus, adjacent circumferential
fibers may abut one another directly, or may be separated but
disposed in such close proximity such that another fiber of the
same width cannot be disposed therebetween without overlap. By
contrast, circumferential fibers 28 disposed in the non-bundled
region 34 are not in direct proximity to one another, such that the
second spacing between individual circumferential fibers 28 is
greater than the width of the fibers themselves. The spacing
between the fibers in each of the bundled regions need not be
identical. Similarly, the spacing of the fibers in the non-bundled
regions need not be identical.
The stents 38, 48, 58 and 68 may comprise any suitable shape for
providing desired support to the stent-graft 20. In one
non-limiting example, shown herein, the stents may comprise a
generally zig-zag shape formed from a single wire comprising a
plurality of substantially straight first segments 82 and second
segments 83 having bent segments disposed therebetween, the bent
segments in the form of proximal apices 81 and distal apices 84. In
one embodiment, each of the proximal apices 81 of the first stent
38 is positioned to overlap with the proximal bundled region 31,
and each of the distal apices 84 of the first stent 38 is
positioned to overlap with the distal bundled region 37, as shown
in FIG. 2. While z-stents are depicted herein, the embodiments are
not limited to z-stents and other stent structures may be used.
Advantageously, by selectively overlapping the proximal apices 81
of the first stent 38 with the proximal bundled region 31, an
enhanced suture attachment site may be provided due to the close
proximity of the circumferential sutures 28 within the proximal
bundle 31. For example, it may be easier to suture the proximal
apices 81 of the stent 38 to the stent-graft 20 in areas where
circumferential fibers are bundled, instead of relatively spaced
apart or lacking entirely. Similarly, by selectively overlapping
the distal apices 84 of the first stent 38 with the distal bundled
region 37, an enhanced suture attachment site may be provided due
within the distal bundled region 37.
Moreover, in the example of FIGS. 1-2, at least two axial fibers
27a and 27b preferably overlap with the various circumferential
fiber bundles at intersections 77. Each of the proximal and distal
apices 81 and 84 of the stent 38 may be aligned with one of the
intersections 77, as shown in FIG. 2. Thus, each of the proximal
and distal apices 81 and 84 of the stent 38 may be secured to the
stent-graft 20 in regions where a circumferential fiber bundled
region meets axial fibers 27, thereby providing selective suture
attachment zones for the stent 38. Notably in this example, there
is a selective axial fiber density along at least a portion of the
stent-graft 20, since axial fibers 27 are intended to only line up
with the proximal and distal apices of a given stent and the
fibers.
As a further advantage, by selectively orienting axial fibers 27
and circumferential fibers 28 at predetermined locations along the
length and circumference of the stent-graft 20, e.g., at specific
points of attachment of proximal and distal stent apices, but not
continuously along the entire stent-graft 20, a significantly
reduced delivery profile may be achieved due to the reduced
presence of fiber material.
Referring still to FIGS. 1-2, in this embodiment the other stents
48, 58 and 68 may be attached to the stent-graft 20 in a similar
manner. In particular, the stent 48 may be positioned to overlap
with the second distinct region 40. The second distinct region 40
may comprise a proximal bundled region 41, intermediate bundled
regions 43 and 45, and a distal bundled region 47, each comprising
at least some circumferential fibers 28 disposed with the first
spacing relative to one another, as shown in FIG. 1. Non-bundled
regions 42, 44 and 46 may be disposed between the various bundled
regions 41, 43, 45 and 47, as shown in FIG. 1. Like the stent 30,
each of the proximal and distal apices 81 and 84 of the stent 48
may be secured to the stent-graft 20 at intersections 77 where a
circumferential fiber bundle meets axial fibers 27. Specifically,
the proximal apices 81 of the stent 48 are attached to the
stent-graft 20 where proximal bundled region 41 meets axial fibers
27, while the distal apices 84 of the stent 48 are attached to the
stent-graft 20 where distal bundled region 47 meets axial fibers
27. Further, the stent 48 may be secured to the stent-graft 20 at
locations in which the substantially straight first segments 82 and
second segments 83 of the stent 48 overlap with the intermediate
bundles 43 and 45. In this manner, multiple specific suture
attachment zones are provided for the stent 48 at the bundled
regions 41, 43, 45 and 47, while the provision of non-bundled
regions 42, 44 and 46 may contribute to reducing the overall
profile of the stent-graft 20 while preferably comprising some
circumferential fibers for distributing loads.
Stent 58 may be positioned to overlap with the third distinct
region 50 in a similar manner that stent 48 is positioned relative
to the second distinct region 40. Specifically, the third distinct
region 50 may comprise a proximal bundled region 51, intermediate
bundled regions 53 and 55, and a distal bundled region 57, while
non-bundled regions 52, 54 and 56 are disposed between the various
bundles regions 51, 53, 55 and 57. Like the stents 30 and 40, each
of the proximal and distal apices 81 and 84 of the stent 58 may be
secured to the stent-graft 20 at intersections 77 where a
circumferential fiber bundle meets axial fibers 27.
Finally, stent 68 may be positioned to overlap with the fourth
distinct region 60 in a similar manner that stent 38 is positioned
relative to the first distinct region 30. Specifically, the fourth
distinct region 60 comprise proximal and distal bundled regions 61
and 67, with non-bundled region 64 disposed therebetween. Like the
stent 30, each of the proximal and distal apices 81 and 84 of the
stent 68 may be secured to the stent-graft 20 at intersections 77
where a circumferential fiber bundle meets axial fibers 27.
Notably, non-bundled spacing regions 39, 49 and 59 are positioned
between the distinct regions 30, 40, 50 and 60, as shown in FIGS.
1-2. Circumferential fibers of the non-bundled spacing regions 39,
49 and 59 may comprise the second spacing relative to one another,
i.e., a greater spacing than in the bundled regions. Thus, there is
a reduction in fiber material in the non-bundled spacing regions
39, 49 and 59, contributing to a reduced delivery profile.
Beneficially, a fiber-reinforced polymer matrix may be provided
that is designed to carry the necessary supporting stents, plus
withstand known loading conditions during long term use in a
particular application, such as in endovascular use.
While intermediate bundled regions are shown only for the second
and third distinct regions 40 and 50, it will be apparent that any
of the various distinct regions 30, 40, 50 and 60 may comprise one
or more intermediate bundled regions, or the various distinct
regions each may omit intermediate bundled regions. Moreover, the
exact placement of the bundled and non-bundled regions may be
varied, e.g., based on desired stent attachment sites, hydrodynamic
forces expected to be imposed upon on the stent-graft 20, and other
factors.
The membrane 25 may be disposed internal or external to the axial
fibers 27 and circumferential fibers 28. In the example of FIGS.
1-2, the membrane 25 is disposed internal to both the axial and
circumferential fibers 27 and 28, but this is not required. In this
instance, the membrane 25 may be formed upon a mandrel, with the
desired circumferential and axial fiber pattern being deposited
externally thereof.
Further, the stents 38, 48, 58 and 68 may be positioned external
and/or internal relative to the membrane 25, as well as external
and/or internal relative to the axial fibers 27 and circumferential
fibers 28. In the example of FIGS. 1-2, the stents 38 and 68 are
disposed internal (dashed lines) relative to the membrane 25, while
the stents 48 and 58 are disposed external of both the membrane 25
and the axial and circumferential fibers 27 and 28. However,
various combinations of internal and external positioning of the
membrane, stents and fibers are possible. Moreover, lamination
and/or embedding of the stents between two membranes may be
provided in lieu of suturing the stents. In the latter embodiment,
selective fiber densities still may be provided for the purpose of
providing reinforcement areas for expected physiological
forces.
During manufacture, the materials may be placed on a mandrel in a
desired orientation. In one exemplary manufacturing step, the
stent-graft 20 may be prepared by mounting the membrane 25 on a
mandrel and then overlaying the axial fibers 27 and circumferential
fibers 28 in a desired orientation. Alternatively, the axial fibers
27 and circumferential fibers 28 may be arranged on the mandrel in
a desired orientation, then the membrane 25 may be disposed over
the fibers. In one other embodiment, the axial fibers 27 and
circumferential fibers 28 may be arranged on the mandrel in a
desired orientation, then the stents 38, 48, 58 and 68 may be laid
over the fibers, and then the membrane 25 may be disposed over the
fibers and the stents. As a further alternative, one membrane may
be placed on the mandrel, then the axial fibers 27 and
circumferential fibers 28 may be deposited onto the first mandrel,
and then a second membrane may be deposited over the first membrane
and the axial and circumferential fibers 27 and 28. Still further,
only some fibers may be applied to the mandrel, such as the
circumferential fibers 28, then the membrane 25 may be deposited
thereon, and then other fibers, such as the axial fibers 27, may be
deposited over the circumferential fibers 28 and the membrane 25.
In sum, various assembly combinations are possible.
Various mechanisms may be used to correctly deposit and align the
axial fibers 27 and circumferential fibers 28 in the desired
orientation, such as automated CNC deposition. The membrane 25 with
axial and circumferential fibers 27 and 28 then may be mounted on a
lathe. The lathe may be rotated at a proper speed, such as 20 rpm,
while applying a dilute polyurethane solution to cover all of the
fibers. The stent-graft 20 then may be cured or dried at about 65
degrees Celsius for about 2 hours while the lathe is rotated at the
desired speed.
The stents then may be secured to the membrane 25, preferably near
one or more intersections 77, as explained above. In one example,
the mandrel used to assemble the materials may comprise pins at
predetermined locations. Various fibers may be arranged around the
pins, such that when the assembled device is removed from the
mandrel, the pins have created bores. The bores created by the
mandrel pins may advantageously provide a predetermined suture
attachment site for subsequent attachment of the stents to the
membrane.
Optionally, the stents may be coupled to the membrane 25 using
polymer encapsulation as the adhesion technique, thereby
eliminating the need for sutures. Regardless of the technique used
to couple the stents to the membrane 25, by selectively orienting
axial fibers 27 and circumferential fibers 28 at predetermined
locations along the length and circumference of the stent-graft 20,
but not continuously along the entire stent-graft 20, a
significantly reduced delivery profile may be achieved.
In one embodiment, the membrane 25 may comprise a polymeric sheet
having a suitable porosity, depending on the application. In one
example, a polymeric sheet may comprise the polyurethane
Thoralon.RTM.. As described in U.S. Pat. No. 6,939,377,
incorporated herein by reference in its entirety, Thoralon.RTM. is
a polyetherurethane urea blended with a siloxane-containing surface
modifying additive. Specifically, the polymer is a mixture of base
polymer BPS-215 and an additive SMA-300. The concentration of
additive may be in the range of 0.5% to 5% by weight of the base
polymer. The BPS-215 component (Thoratec.RTM. Corporation,
Pleasanton, Calif.) is a segmented polyether urethane urea
containing a soft segment and a hard segment. The soft segment is
made of polytetramethylene oxide (PTMO), and the hard segment is
made from the reaction of 4,4'-diphenylmethane diisocyanate (MDI)
and ethylene diamine (ED). The SMA-300 component (Thoratec.RTM.
Corporation, Pleasanton, Calif.) is a polyurethane comprising
polydimethylsiloxane as a soft segment and the reaction product of
MDI and 1,4-butanediol as a hard segment. A porous polymeric sheet
can be formed from these two components by dissolving the base
polymer and additive in a solvent such as dimethylacetamide (DMAC)
and solidifying the mixture by solvent casting or by coagulation in
a liquid that is a non-solvent for the base polymer and
additive.
Thoralon.RTM. has been used in certain vascular applications and is
characterized by thromboresistance, high tensile strength, low
water absorption, low critical surface tension, and good flex life.
Thoralon.RTM. is believed to be biostable and to be useful in vivo
in long term blood contacting applications requiring biostability
and leak resistance. Because of its flexibility, Thoralon.RTM. may
be useful in larger vessels, such as the abdominal aorta, where
elasticity and compliance are beneficial.
Further, Thoralon.RTM. may also be used as a drug delivery vehicle,
for example, to deliver one or more therapeutic agents. The
therapeutic agents may be coated onto or contained within a porous
outer layer of the membrane 25 for sustained release subsequent to
an implantation procedure and may be used, for example, to promote
intimal cell in-growth.
While Thoralon.RTM. is one example, the membrane 25 may comprise
other materials. In addition to, or in lieu of, a polyurethane such
as Thoralon.RTM., the membrane 25 may comprise any biocompatible
polymeric material including non-porous or substantially non-porous
polyurethanes, PTFE, expanded PTFE (ePTFE), polyethylene
tetraphthalate (PET), aliphatic polyoxaesters, polylactides,
polycaprolactones, hydrogels, and other non-polymeric
materials.
The stent-graft 20 may be used in a wide range of procedures, for
example, to treat an aneurysm, stenosis, dissection or other
condition. As known in the art, stents 38, 48, 58 and 68 have
compressed, reduced diameter delivery states in which the
stent-graft 20 may be advanced to a target location within a
vessel, duct or other anatomical site, and further have expanded
states, as shown in FIG. 2, in which they may be configured to
apply a radially outward force upon the vessel, duct or other
target location, e.g., to maintain patency within a passageway,
while the lumen 29 is suitable for carrying fluid though the
stent-graft 20. The stent-graft 20 may be designed specifically for
treating abdominal or thoracic aneurysms or dissections. Moreover,
while a single lumen device is shown, the principles used herein
may be used in connection with bifurcated stent-grafts.
The stents 38, 48, 58 and 68 may be made from numerous metals and
alloys. In one example, the stents 38, 48, 58 and 68 comprise a
shape-memory material such as a nickel-titanium alloy ("nitinol").
Moreover, while generally zig-zag shaped stents are shown, the
structure of the stents 38, 48, 58 and 68 may be formed in a
variety of ways to provide a suitable intraluminal support
structure. For example, one or more stents 30 may be made from a
woven wire structure, a laser-cut cannula, individual
interconnected rings, or another pattern or design. Depending on
the stent structure employed, the position of the fiber bundles may
be varied to provide appropriate suture attachment sites in a
manner similar to the zig-zag stent example of FIGS. 1-2.
Referring now to FIGS. 3-8, various alternative arrangements of
components, in accordance with principles above, are shown and
described. For example, in FIG. 3, an alternative stent-graft 120
comprises a membrane 125, stents 138 and 178, and a plurality of
angled axial fibers 127. The membrane 125 is similar to the
membrane 25 of FIGS. 1-2, and the stents 138 and 178 are similar to
the stent 38 of FIGS. 1-2. In this example, the stent 178 is
affixed to the proximal end 122 of the membrane 125 and has first
and second substantially straight segments 182 and 183 separated by
proximal and distal apices 181 and 184. Each of the distal apices
184 may be connected to the proximal end 122 of the membrane 125,
as shown in FIG. 3. Furthermore, the stent 138 is coupled to the
membrane 125 using a plurality of sutures 188 or other attachment
methods as discussed. A plurality of circumferential fiber bundled
regions 131, 133, 135 and 137, shown in FIG. 4, may be used in the
embodiment of FIG. 3 to provide attachment zones for the sutures
188 to the membrane 125 in the manner noted above in FIGS. 1-2.
In this example, each of the angled axial fibers 127 are disposed
around one of the distal apices 184 of the stent 178. The angled
axial fibers 127 therefore each form first and second segments 127a
and 127b that extend in a distal direction away from the stent 178.
The first and second segments 127a and 127b of the angled axial
fibers 127 may extend at an angle relative to a longitudinal axis L
of the stent-graft. For example, the angle may range from about 1
to about 15 degrees, as depicted in FIG. 3. Notably, such angled
axial fibers segments 127a and 127b may be more compliant than the
axial and circumferential fibers 27 and 28 shown above, thereby
selectively providing compliant support at predetermined
locations.
Referring now to FIG. 4, an exemplary alternative stent-graft 120'
is similar to stent-graft 120, and comprises a membrane 125 and
stents 138 and 178. A plurality of axial fibers, such as angled
axial fibers 127 of FIG. 3, may be employed but are omitted in the
illustration. In this example, a plurality of circumferential
fibers 128 is provided. Unlike the circumferential sutures 28 of
FIGS. 1-2, which are generally perpendicular to the longitudinal
axis L of the stent-graft, the circumferential fibers 128 are
disposed at angle .alpha..sub.1 relative to the longitudinal axis L
of the stent-graft, as shown in FIG. 4. In one example, the angle
.alpha..sub.1 may range from about 70 to about 89 degrees. Like the
angled axial fibers segments 127a and 127b of FIG. 3, the angled
circumferential fibers 128 of FIG. 4 may be more compliant than the
circumferential fibers 28, thereby selectively providing compliant
support at predetermined locations.
Referring now to FIGS. 5-7, various alternative stent-grafts are
shown. Notably, in FIGS. 5-7, various circumferential, axial and
angled fibers are depicted with dashed lines for illustrative
purposes only, but it is preferred that such circumferential, axial
and angled fibers are generally formed from continuous filaments.
In FIG. 5, an alternative stent-graft is similar to stent-graft
120, with like reference numerals labeled accordingly. In FIG. 5,
at least two axial fibers 227a and 227b preferably overlap with the
various circumferential fiber bundled regions 131, 133, 135 and 137
at intersections 177. Each of the proximal apices 181 of the stent
138 may be aligned with one of the intersections 177, as shown in
FIG. 5. Thus, each of the proximal apices 181 of the stent 138 may
be secured to the stent-graft 220 in regions where a
circumferential fiber bundle meets axial fibers 227a and 227b,
thereby permitting a significantly enhanced suture attachment zone
for at least the proximal apices 181 of the stent 38. Optionally,
additional axial fibers may be provided that coincide with the
distal apices 184 in a similar manner.
Referring now to FIG. 6, an alternative stent-graft 220' is similar
to the stent-graft 220 of FIG. 5. However, in FIG. 6, the plurality
of circumferential bundled regions 131, 133, 135 and 137 are
omitted, and a plurality of angled circumferential fibers 228 are
utilized. The angled circumferential fibers 228 are parallel to one
another, but are disposed at an angle .alpha..sub.2 relative to the
longitudinal axis L of the stent-graft 220'. In one example, the
angle .alpha..sub.2 is between about 70 to about 89 degrees.
Moreover, in this example, the angled circumferential fibers 228
may be wound at between about 10 to about 30 threads per inch
(TPI). In FIG. 6, sutures 188 may be coupled to the membrane 125
along multiple parts of each segment 182 and 183 of the stent 138,
as well as at each of the proximal and distal apices 181 and
184.
Referring now to FIG. 7, an alternative stent-graft 220'' is
substantially identical to the stent-graft 220' of FIG. 6. However,
in FIG. 7, angled circumferential fibers 228' may be wound at
between about 30 to about 50 threads per inch (TPI). Therefore, the
closer bundling of angled circumferential fibers 228'' in FIG. 7
may provide an enhanced site for attaching sutures 188 to the
membrane 125.
Notably, in FIGS. 6-7, the angled circumferential fibers 228 are
bundled together along a distinct region 230, which generally
overlaps with the stent 138. Non-bundled regions 239 and 249 may
exist proximal and distal to the distinct region 230, i.e., in
regions where a stent is not present.
Referring now to FIG. 8, a proximal portion of an alternative
stent-graft 320 is shown and described. In this example, the
stent-graft 320 comprises a bare proximal stent 360 that is coupled
to a membrane 325. The stent 360 may be manufactured from a
continuous cylinder into which a pattern may be cut by a laser or
by chemical etching to produce slits in the wall of the cylinder.
The resulting structure may then be heat set to give it a desired
final configuration. As shown in FIG. 8, the configuration may
include a shape having a series of proximal apices and a series of
distal apices. A proximal end 362 of the stent 360 may comprise
multiple adjacent proximal apices 362a and 362b, while a distal end
364 of the may comprise multiple adjacent distal apices 388 having
bores 389 formed therein, as shown in FIG. 8. In FIG. 4, a first
proximal apex 362a may comprise an end region 370 having a bore 371
formed therein. A second, adjacent proximal apex 362b may comprise
an end region 375 having an integral barb 377 formed therein.
Alternatively, both proximal apices 362a and 362b may comprise
integral barbs 377.
The stent 360 may comprise multiple angled strut segments disposed
between a proximal apex 362a or 362b, and a corresponding distal
apex 364a. By way of example, first and second angled strut
segments 367 and 368 may be provided. A first angled strut segments
367 may meet with an adjacent second angled strut segment 368,
thereby forming a transition region 380. Expansion of the stent 360
is at least partly provided by the angled strut segments 367 and
368, which may be substantially parallel to one another in a
compressed state, but may tend to bow outward away from one another
in the expanded state shown in FIG. 8. Each transition region 380
may comprise a larger surface area relative to the angled segments,
and at least one barb 382 may be disposed in at least one of the
transition regions 380.
Each of the distal apices 388 of the stent 380 may be coupled to a
proximal end 322 of the membrane 325, for example, using one or
more sutures that are looped through the graft membrane 325 and the
bores 389 of the stent 360. In this manner, the stent 360 may be
used as an attachment stent for endovascular graft fixation. For
example, the membrane 325 may overlap with an aneurysm to seal off
fluid flow into the aneurysm, while the proximal end 362 of the
stent 360 may extend in a proximal direction away from the graft
material, e.g., to engage a healthy portion of a vessel wall away
from a diseased portion of the aneurysm. As will be apparent, one
or more additional stents may be coupled to an inner or outer
surface of the membrane 325, i.e., at a location distal to the
stent 360, to help maintain patency throughout the graft
material.
In FIG. 8, a plurality of axial fibers 327 and circumferential
fibers 328 are provided, either inside or outside of the membrane
325. The plurality of axial fibers 327 and circumferential fibers
328 may be provided in accordance with the plurality of axial
fibers 27 and the plurality of circumferential fibers 28, as shown
in FIGS. 1-2 above.
Further, in FIG. 8, a plurality of angled axial fiber bundles
327a-327d are shown positioned external to the membrane 325, though
additional angled fiber bundles that are not depicted extend around
the full circumference of the membrane 325. Each of the angled
axial fiber bundles 327a-327d comprises multiple segments 391-394,
though greater or fewer segments may be employed. Two individual
fibers within each bundle 327a-327d may be looped through the bore
389 at a distal apex 388 of the stent 360, and therefore, the two
individual fibers extend distally away from the stent 360 forming
the four segments 391-394. The four segments 391-394 may fan
outward relative to one another, i.e., become further spaced apart
relative to each other as they extend in a proximal to distal
direction, as shown in FIG. 8.
It is believed that by providing axial fiber bundles 327a-327d
coupled to, and extending distally from, the stent 360 in the
manner shown, wherein multiple segments 391-394 fan outward
relative to one another, the fibers may be oriented in a manner
that reinforces strength characteristics of stent-graft 320 while
maintaining its lower profile. In particular, it is believed that
such a structure of FIG. 8 may selectively reinforce the membrane
325 and allow the stent-graft 320 to withstand physiological fluid
flow in a proximal to distal direction.
Referring now to FIGS. 9A-9C, an alternative stent-graft 420
borrows various principles from the above-described stent-grafts,
and comprises a membrane 425 having proximal and distal ends 422
and 424 and a lumen 429 extending therebetween. In one optional
method step, depicted in FIG. 9A, multiple holes 490 may be drilled
around the circumference of the membrane 425, thereby forming a
plurality of rows 491. In one embodiment, about forty rows 491 may
be formed. Then, a corresponding number of axial fibers 427 may be
coupled to the membrane 425, as shown in FIG. 9B. For example, each
axial fiber 427 may be looped through the holes 490 of a particular
row 491. Alternatively, the holes 490 may be omitted and a desired
number of axial fibers 427 may be arranged internal or external to
or within the membrane 425.
In FIG. 9B, after the axial fibers 427 have been coupled to the
membrane 425, a proximal attachment stent 460 may be disposed
external to the axial fibers 427. The stent 460 may be similar to
the stent 360 described in FIG. 8, and may comprises a plurality of
proximal and distal apices 462 and 464. A plurality of angled axial
fiber bundles 427a-427d may be coupled to the stent 460 external to
the membrane 425, as shown in FIGS. 9B-9C. Each of the angled axial
fiber bundles 427a-427d comprises multiple segments 491-494, though
greater or fewer segments may be employed. Two individual fibers
within each bundle 427a-427d may be looped through bores at a
distal apex 464 of the stent 460, in the manner shown in FIG. 8
above, and therefore the two individual fibers extend distally away
from the stent 460 forming the four segments 491-494. The four
segments 491-494 may fan outward relative to one another, i.e.,
become further spaced apart relative to each other as they extend
in a proximal to distal direction, as shown in FIGS. 9B-9C.
As shown in FIG. 9C, in a next step, a plurality of circumferential
fibers 428 then may be arranged outside of the membrane 425 and the
angled axial fiber bundles 427a-427d at locations distal to the
proximal stent 460. The plurality of circumferential fibers 428 may
be provided in accordance with the plurality of circumferential
fibers 28, as shown in FIGS. 1-2. In a final step, one or more
stents 438, such as zig-zag shaped stents provided as described
above, may be arranged over the plurality of circumferential fibers
428 at locations distal to the proximal stent 460, as shown in FIG.
9C. The stent 438 may be secured to the membrane 425. The
stent-graft 420 then may be prepared by mounting the membrane 425
on a lathe. The lathe may be rotated at a proper speed, such as 20
rpm, while applying a dilute polyurethane solution to cover all of
the fibers disposed distal to the proximal stent 460. The
stent-graft 420 then may be cured at about 65 degrees Celsius for
about 2 hours while the lathe is rotated at the desired speed.
Advantageously, like the stent-grafts above, it is believed that
the stent-graft 420 of FIGS. 9A-9C may provide a selectively
reinforced membrane 425 that may better withstand physiological
fluid flow in a proximal to distal direction. Further, by
selectively orienting axial fibers 427, angled axial fiber bundles
427a-427d, and circumferential fibers 428 at predetermined
locations along the length and circumference of the stent-graft
420, but not continuously along the stent-graft 420, a
significantly reduced delivery profile may be achieved.
Referring to FIG. 10, in lieu of the generally axial and
circumferential fibers 27 and 28 shown above, a further alternative
stent-graft 520 may comprise a plurality of first fibers 527 and a
plurality of second fibers 528, neither of which are substantially
parallel or perpendicular to the longitudinal axis L of the
prosthesis. The plurality of first fibers 527 and the plurality of
second fibers 528 may be overlapping, but not interwoven. Such
angled first and second fibers 527 and 528 may be more compliant
than the axial and circumferential fibers 27 and 28 shown above,
but still may be selectively arranged in a manner that may
beneficially handle physiological loads, facilitate stent
attachment to the membrane 525, and reduce the overall profile of
the stent-graft 520, in the manner described above.
While various embodiments of the invention have been described, it
will be apparent to those of ordinary skill in the art that many
more embodiments and implementations are possible within the scope
of the invention. Accordingly, the invention is not to be
restricted except in light of the attached claims and their
equivalents. Moreover, the advantages described herein are not
necessarily the only advantages of the invention and it is not
necessarily expected that every embodiment of the invention will
achieve all of the advantages described.
* * * * *